The Mirror effect splits the image along a line and reflects one side onto the other.

Reflection Center

The position of the line about which the reflection occurs.

Reflection Angle

The angle of the line about which the reflection occurs. An angle of 0° reflects the left side onto the right. An angle of 90° reflects the top onto the bottom.

Note: You can directly manipulate the Mirror effect in the Program monitor. Click the Transform icon  and then drag the adjustment handle.